284
THE ESSEX NATURALIST
References
Coles, J. W. (1960). Free-living Nematodes from Skippers Island. Essex
Nat, 30 (3): 204-207.
-------- (1965. A Critical Review of the Marine Nematode Genus
Euchromadora de Man, 1886. Bull. Brit. Mus. nat. Hist. (Zoology),
12 (5): 157-194.
-------- (1965a). Two New Species of Marine Nematodes from the British
coast. Ann. Mag. nat. Hist. (13), 8: 65-70.
Inglis, W. G. & Coles, J. W. (1961). The species of Rhabditis found in
rotting Seaweed on British beaches. Bull. Brit. Mus. nat. Hist.
(Zoology), 7 (6): 320-333.
Nisbet, R. H. (1961). Marine Biology at Skipper's Island. Essex Nat.,
30 (4): 247-253.
Schuurmans Stekhoven, J. H., Jr. (1935). Nematoda errantia. Tierw.
N.—u. Ostsee, 5b : 173 pp. (Lief. 28).
A Study of the mite Parasitus bomborum
By Peter D. Stebbing
While studying bumblebees I found that they were commonly
infested by a small brown mite known as Parasitus bomborum
Oudemans, 1902. References have been made to this mite by
Step (1932) and Free and Butler (1959), but in neither publication
was there mention of the lifecycle nor was there certainty about its
relationship to the bumblebee.
The mite was first recorded by Oudemans in 1902 who found
them in a nest of Bombus terrestris. P. bomborum, as it is referred
to here, has not been specifically indentified and in fact four species
of mite may have been concerned, all of which may be found
both on the body of the bee and in the nest itself. In an attempt
to clarify the life-cycle I wrote to Mr D. C. Lee of Rothamsted
Experimental Station, who informed me that the mites pass
through the following stages in their metamorphosis: —egg
(Figure 1A is thought to be that of P. bomborum), larva (not
illustrated and as yet unobserved by the author), protonymph
(Figures 1B and 1C show early and late protonymphs respec-
tively), deutonymph (Figure 1D), adult (not drawn). With this
information and some of my own observations I constructed a
hypothetical life-cycle (Figure 2). I then set out to confirm as
much of it as I could. The following observations confirmed part
of the life-cycle that I proposed.
On 8th June 1964 I collected a selection of flowers to make
observations on their pollen (viz. Dandelion—Taraxacum
officinale, Daffodil—Narcissus sp., Tulip—Tulipa sp., and White
Deadnettle—Lamium album). Soon after placing them on
the bench I noticed a specimen of Parasitus bomborum leaving
one of the flower heads and it seems likely that flowers